From the first waves of the epidemic, the research team observed that the SARS-CoV-2 did not merely attack the lungs: it also caused “endotheliopathy”, a dysfunction of the inner wall of the blood vessels that play a key role in regulating blood coagulation, leading to often fatal microthromboses.

In this study, the scientists attempted to understand the impact of different treatments for severe Covid-19 on the blood vessels and coagulation.

They monitored 375 patients with COVID-19, some in intensive care, at the Hôpital Européen Georges-Pompidou. Thanks to the analysis of blood samples and a thrombin generation test (a key enzyme in the formation of blood clots), the scientists were able to measure the impact of the virus and various treatments for its most serious forms on the blood’s ability to coagulate.

Their main discovery: dexamethasone, a corticoid whose effectiveness has been proven for patients with severe forms of COVID-19 associated with respiratory complications, significantly reduces markers of endothelial damage and thrombin production. It directly protects endothelial cells against the cytokine storm caused by the virus, while heparin (a commonly used anticoagulant) does not have this effect.

These findings reinforce the idea that vascular inflammation is at the heart of COVID-19 complications, far beyond mere lung damage. Finally, it shows that the intensity of plasma-induced coagulation anomalies in patients is strongly correlated with a risk of death.

“Our experimental model has shown that dexamethasone acts not only as a general anti-inflammatory steroid, but also as a direct protector of the vessels,” explains David Smadja, coordinator of the study.

These results shed light on the observed benefits of dexamethasone in clinical trials and support its central role in the management of severe forms of COVID-19, by limiting thrombotic drifts related to vascular involvement.

Reference

Dexamethasone Suppresses Endotheliopathy and Endothelial-Induced Coagulopathy in COVID-19
Aurélien Philippe, Romy Younan, Nicolas Gendron, Nicolas Peron, Xavier Loyer, Jeanne Rancic, Caroline Hauw-Berlemont, Paul Billoir, Bertrand Hermann, Lina Khider, Olivier Sanchez, Gilles Chatelier, Chantal M Boulanger, Jean-Luc Diehl and David M. Smadja.
Arterioscler Thromb Vasc Biol., 2025 | DOI: 10.1161/ATVBAHA.125.322774

Translated by MA translation students, Master’s in Language Industry and Specialised Translation, Université Paris Cité, 2026